Architecture

For the purpose of django-rq-mail, it implements the concept of WaitingQueue
which delays the processing of a job with a timestamp.

The default behavior of rq is to process jobs via BLPOP which
blocks the connection when there are no elements to pop from any of the given queues.
With this behavior there is no way to delays the processing of a job and when it’s failing
rq pushs it in a failed queue.
Of course, you can requeue this job later but there is no fallback mechanism.

In django-rq-mail you can define fallback steps (in seconds) to retry a job until
it’s not failing. When a job has been tested on each steps we reintroduce
the default behavior of rq on pushing it in the failed queue.

Each steps will create a waiting queue and when a job is failing we take the
current timestamp with the delta to retry it in the future.

This mechanism is possible with ZADD which
adds a serialized job in the queue with a score and ZREVRANGEBYSCORE
to return all the elements in the sorted set with a score between max (current timestamp) and min.

As you may understood, we have dropped the default blocking behavior
to replace it by a daemon which is running each seconds.

Installation

Either check out the package from GitHub or it pull from a release via PyPI

pip install django-rq-mail

Add ‘rq_mail’ to your INSTALLED_APPS

INSTALLED_APPS = (
'rq_mail',
)

to use the rq_mail command (via Django commandline) shipped by django-rq-mail.

This command is a minimal integration of rq into Django to launch the
Dispatcher.

Define EMAIL_BACKEND

EMAIL_BACKEND = 'rq_mail.backends.RqBackend'

Define RQ_MAIL_EMAIL_BACKEND the backend used to send your emails, for example

RQ_MAIL_EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'

Utilisation

Once you have installed it, you can run python manage.py rq_mail from your shell.

Configuration

RQ_MAIL_PREFIX

The prefix used to name all queues created by django-rq-mail.

RQ_MAIL_MAIN_QUEUE

The name of the main queue.

RQ_MAIL_EMAIL_BACKEND

The email backend used to send emails when they are processed in the background.

RQ_MAIL_REDIS_HOST

The Redis host used to connect.

RQ_MAIL_REDIS_PORT

The Redis port used to connect.

RQ_MAIL_REDIS_DB

The Redis database used to connect.

RQ_MAIL_REDIS_PASSWORD

The Redis password used to connect.

RQ_MAIL_FALLBACK_STEPS

A simple list of timing to create waiting queues.

You can define as much steps as you want, each will be transformed to a queue.
So if you define 10 steps, you will allow a message to fail 10 times until it
will go in the failed queue.